The additional research conducted as part of this program will exceed the capacity of the existing Flow Cytometry Facility in the Immunobiology Section at Yale University. This core facility is intended to increase the efficiency of use of the two existing flow cytometers. A FACS operator will be employed to: 1. Become trained in the use of the FACStar Plus cell sorter, and extend the hours during which this machine is usable by working on a 'flexitime' basis, co-ordinated with the schedule of the principal FACStar Plus operator. 2. To allow use of the FACScan analytical flow cytometer for untrained personnel. At present this instrument is restricted to trained individuals, and is therefore unavailable to occasional users or to new members of the Program.